High Nb Contents Research Articles

Influence of Nb Content on Microstructure and Mechanical Properties of a 7%Ni Steel

The influence of Nb content on the microstructure and cryogenic mechanical properties of a 7%Ni steel was investigated within the Nb content range from 0 to 0.05%. The microstructure was characterized by optical microscope, scanning electron microscope, transmission electron microscopy and X-ray diffraction, and the low-temperature mechanical property tests were conducted. The Nb addition can effectively refine the prior austenite grains and microstructure of the steel. Fine niobium precipitates with a diameter of about 10–50 nm were observed. They tend to be spherical and locate mainly in the vicinity of grain boundaries. Although there are considerable amounts of reversed austenite forming at grain boundaries in the specimen containing the highest Nb content, no Nb element was detected in such reversed austenite, which implies that Nb element did not affect the formation of the reversed austenite directly. Mechanical test results suggest that the strength of the 7%Ni steel is not simply in relation to the prior austenite grain size, but also depends on the amount of reversed austenite. On the other hand, the grain refinement, enhanced with increasing Nb content, has a good effect on cryogenic toughness.

Effect of Nb content on thermal stability, mechanical and corrosion behaviors of hypoeutectic CoCrFeNiNbχ high-entropy alloys

Abstract

Comparison of Mechanical Properties and Microstructure of Annealed and Quenched Ti-Nb Alloys

The effect of Nb content on microstructure, mechanical properties and phase formation in annealed and quenched binary Ti-Nb alloys were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. The content of Nb varied in the range 0-37 mass % leading to significant changes in the microstructure. The annealed and furnace-cooled binary Ti-Nb samples exhibited HCP martensitic α` phase at a Nb content below 14 mass % and stable BCC β phase at higher contents of Nb. The structure of the quenched samples changed with increase of Nb content in the following order: coarse primary martensite → fine acicular (α`+α``) martensite → single β phase structure. The mechanical properties of alloys strongly depended on the Nb content and type of the dominating phase.

Late Carboniferous to Early Permian magmatic pulses in the Uliastai continental margin linked to slab rollback: Implications for evolution of the Central Asian Orogenic Belt

The Paleo Asian Ocean underwent a protracted closure history during Late Paleozoic. Here we investigate the magmatic evolution during this process based on a detailed study in the Baiyinwula region along the Uliastai continental margin. The major rock types in this area are Late Carboniferous-Early Permian volcanic sequences and coeval intrusions. We identified four stages of magmatic evolution based on the diverse assemblages and their precise isotopic ages. The first stage is represented by andesites with a zircon 206Pb/238U age of ca. 326±12Ma. These rocks are metaluminous to weakly peraluminous, high-K calc-alkaline, and possess high Na2O/K2O ratios in the range of 1.23 to 2.45. They also display enrichment of large ion lithophile elements (LILE) and depletion of high field strength elements (HFSE), with markedly positive zircon εHf (t) varying from 8.1 to 15.6.The geochemical features of these andesites are similar to those of typical arc volcanic rocks. The second stage includes granodiorites emplaced at 318.6+1.8Ma. The rocks are high-K calc-alkaline with A/CNK values ranging from 0.95 to 1.06, and show enrichment in LILE and depletion in HFSE. They show geochemical affinities to adakites, with high Sr and low Y and Yb contents, indicating magma derivation from thickened lower crust. Zircon grains from these rocks display positive initial εHf (t) values ranging from 11.1 to 14.6 with corresponding two-stage Hf model ages (TDM2) of 394–622Ma. The third stage consists of syenogranite together with a volcanic suite ranging in composition from rhyolite todacite, which formed during 303.4±1.2 to 285.1±2.2Ma. They possess elevated silica and alkali contents, high FeOt/MgO and Ga/Al ratios, low Al2O3, MgO and CaO contents, and high Rb, Y, Nb, Ce, Zr, Y, and Ga contents, strong negative Ba, Sr and Eu anomalies, showing I- to A-type granitic affinities. Zircons in these rocks show elevated Hf isotopic compositions (εHf (t)=9.9 to 14.6) with TDM2 varying from 324 to 673Ma. The fourth magmatic pulse is represented by K-feldspar granite with zircon U-Pb ages from 283.2±1.9Ma to 280.0±1.4Ma, and typical alkalic A-type granite geochemistry. These rocks possess positive εHf (t) values in the range of 9.7 to15.2, and a restricted range of Hf model age from 327 to 684Ma. The magmatic rocks from the four stages show comparable εHf (t) and T2DM, suggesting that the magmas were derived from the same evolving mantle-derived source. We propose a tectonic model linking the evolution of the magmatism with the closure of the Paleo Asian Ocean that involved the following stages. The andesites were formed during the initial oceanic subduction stage with magma sourced from the metasomatized lithospheric mantle. Stage 2 adakite-like rocks were derived from subduction-induced thickened crust. Subsequent slab rollback resulted in asthenospheric upwelling and melting of residual juvenile crust to generate the I- and A- type syenogranite, rhyolite and dacite suite, finally followed by the A-type K-feldspar granite.

Ancient tin production: Slags from the Iron Age Carvalhelhos hillfort (NW Iberian Peninsula)

Provenance and production of tin in the Ancient World has since long been a major topic of discussion among archaeologists. In Western Europe, where significant tin ore (cassiterite) deposits are known, only a few remains of ancient tin production, such as tin slags, have been detected. In the present work, elemental and microstructural analyses by WDXRF, SEM-EDS and XRD were performed on recently recognised tin slags from the Iron Age Carvalhelhos hillfort located in NW Iberia, a territory that represents the largest extension with tin mineralisation in Western Europe. Elemental and microstructural characterisation of cassiterite collected in a pilot field survey in the region of the hillfort are presented and discussed, as well as two ceramic fragments that could be part of a smelting structure and an iron slag from the settlement. Results show that the tin slags have variable but high contents in Sn, similarly to Pre-Medieval tin slags found in other Western European areas, but also high contents of Ta and Nb, which specifically distinguish them from other tin slags, such as those found in SW Britain. Tin ores from the hillfort region frequently have Ta and Nb in cassiterite solid solution or as inclusions of columbite group minerals, relating well with the Carvalhelhos tin slags. Up to present, the Carvalhelhos slags are amongst the very few ancient tin slags known in Western Europe, and their study can contribute to a better knowledge on ancient tin sources and trade routes.

Enrichment of Bi-Be-Mo-Cd-Pb-Nb-Ga, REEs and Y in the Permian coals of the Huainan Coalfield, Anhui, China

This paper presents new data concerning the geochemistry and distribution of the Bi-Be-Mo-Cd-Pb-Nb-Ga, and REY in the Panyi, Xieqiao, Xinji, Zhuji, and Zhuji Xi coals of the Huainan Coalfield. The results indicate that the Huainan bituminous coals were characterized by medium ash yields and low to medium sulfur contents. The mineral assemblage present in the Huainan coals is mainly made up of quartz, kaolinite, pyrite, and calcite. The minerals, ash yield, sulfur contents, volatile matter contents, Sr/Ba, SiO2/Al2O3, and (CaO + MgO + Fe2O3)/(SiO2 + Al2O3) ratio varied significantly in the Huainan Coalfield, which are attributed mainly to vertical variation in the depositional environment. These coals contain high contents of Ga, Nb, Mo, Be, Pb, Ba, SiO2, Fe2O3, TiO2, CaO, Na2O, Al2O3, MnO, K2O, and MgO, especially in the marine-influenced environment coals. The average contents of Ga, Nb, Mo, Be, and REY are higher than those of world-wide bituminous coals, thus a hidden treasure is a yet to-be-realized new economic potential. The Bi, Be, Mo, Nb, Ga, and REY have mixed organic-inorganic affinity, while Cd and Pb mainly have an organic affinity in the Huainan coals. Compared to the average Chinese coals, the REY are enriched in the Panyi, Xieqiao, and Xinji coals, slightly lower in the Zhuji coals and depleted in the Zhuji Xi coals. Compared to the upper continental crust, REY in the Huainan coal samples has medium-REY and light-REY enrichment. The average concentration of oxides (ash basis) of the rare earth elements and Y in the Panyi (on average 1120.3 μg/g), Xieqiao (1287.7 μg/g), Xinji (1148.7 μg/g), and Zhuji (1025.1 μg/g) coals are higher than the cut-off grade for industrial deposits of these elements and thus, the Huainan coals are considered as raw materials for the recovery of rare earth elements.

The Application of 40Ti-35Ni-25Nb Filler Foil in Brazing Commercially Pure Titanium

The clad ternary 40Ti-35Ni-25Nb (wt %) foil has been applied in brazing commercially pure titanium (CP-Ti). The wavelength dispersive spectroscope (WDS) was utilized for quantitative chemical analyses of various phases/structures, and electron back scattered diffraction (EBSD) was used for crystallographic analyses in the brazed joint. The microstructure of brazed joint relies on the Nb and Ni distributions across the joint. For the β-Ti alloyed with high Nb and low Ni contents, the brazed zone (BZ), consisting of the stabilized β-Ti at room temperature. In contrast, eutectoid decomposition of the β-Ti into Ti2Ni and α-Ti is widely observed in the transition zone (TZ) of the joint. Although average shear strengths of joints brazed at different temperatures are approximately the same level, their standard deviations decreased with increasing the brazing temperature. The presence of inherent brittle Ti2Ni intermetallics results in higher standard deviation in shear test. Because the Ni content is lowered in TZ at a higher brazing temperature, the amount of eutectoid is decreased in TZ. The fracture location is changed from TZ into BZ mixed with α and β-Ti.

Geochemical types of subvolcanic dacite – rhyolite complexes from the сentral part of the Vedlozero-Segozero greenstone belt (Karelian Craton)

The paper presents the results of detailed geological, petrographic and geochemical studies of Archean acidic subvolcanic rocks from the Koikary domain located in the central part of the Vedlozero-Segozero greenstone belt. Three petrologically contrasting groups are clearly distinguished in the investigated dacite-rhyolite association: 1) dacite with high content of Cr, Ni, Ti, Nb, and heavy REE, which are characterized by εNd (2935 Ma) from +0.72 to +2.93 and contain porphyritic phenocrysts of several generations; 2) rhyolite with a strongly fractionated REE distribution, negative anomalies in Nb, Sr and Ti, and with εNd (2935 Ma) from +1.15 to +3.37; 3) dacite and rhyolite with a moderately fractionated REE distribution, negative anomalies in Nb, Sr and Ti, and with εNd (2935 Ma) = –6.47. The above mentioned features of the rocks reflect the contrasting conditions of generation of acidic subvolcanic rocks in the Koikary domain and mark different time stages of the greenstone belt development.

Petrology, mineralogy and geochemistry of the Lower Cretaceous oil-prone coal and host rocks from the Laoheishan Basin, northeast China

The coal and host rocks (mainly oil shale partings) in the Laoheishan basin (NE China) are oil-prone. This study uses petrological, mineralogical and geochemical analyses to determine the reasons of high oil yield in the coal, and the origin and modes of occurrence of the minerals and elements in the coal and oil shale partings. The obtained data show that this sub-bituminous B coal has higher oil yield (av. 10%) than oil shale partings (av. 5.7%), consistent with a higher hydrogen content in the coal. This oil-prone coal has potential for comprehensive utilization due to the relatively high gross calorific value (av. 17.23 MJ/kg) in the semi-coke. The maceral composition suggests that the relatively high hydrogen content in the coal is mainly caused by higher resinite content. Palynological analysis of coal and oil shale partings mainly proved the presence of gymnosperms and ferns, revealing that the paleovegetation is dominated by lygodiacean-/osmundacean ground ferns and cupressaceaen/taxodiaceaen canopy trees, these canopy trees would have provided abundant hydrogen rich components (e.g. resin) to the paleomire. All the identified sporopollen suggests a warm-humid subtropical paleoclimate.Minerals in the coal include kaolinite, quartz, illite (and/or illite/smectite), chlorite, feldspar, calcite, and traces of pyrite, rutile and zircon, similar to the oil shale partings. Most of the minerals (quartz, feldspar, clay minerals, rutile and zircon) occur in layers within detrovitrinite and probably are of detrital origin. Pyrite and calcite are of epigenetic origin and probably derived from hydrothermal fluids. Compared with average Chinese coal, the Laoheishan coal is enriched in Zr, Nb, In and Sb. Zirconium and Nb mainly occur in zircon. Indium is both organically and inorganically associated, whereas antimony largely occurs in pyrite. REY (rare earth elements and yttrium) distribution patterns of coals and oil shale partings are dominated by Heavy-REY enrichment, whereas roof and floor samples are Medium-REY enriched. The M-HREY enrichment is probably caused by low-temperature hydrothermal fluids. The sedimentary input is the major controlling factor of geochemical patterns in coal and host rocks. The source rocks are probably felsic-intermediate igneous rocks from the surrounding basement, as indicated by relatively high Al2O3/TiO2 ratios (7–38), cross-plot between Zr/Ti and Nb/Y, negative Eu anomalies (0.28–0.96), the presence of K-feldspar and plagioclase, and lithic fragment types (such as granite and andesite) in the samples. In addition, source rocks of sediments have caused high Zr and Nb concentrations in the coal.

Anomalous magnetic and spin glass behavior in Nb-substituted LaCo1−xNbxO3

We report the structural, magnetic, transport, and electronic properties of Nb-substituted ${\mathrm{LaCo}}_{1\ensuremath{-}x}{\mathrm{Nb}}_{x}{\mathrm{O}}_{3}$ ($x=0--0.2$). The Rietveld refinement of x-ray diffraction data demonstrate structural phase transitions from rhombohedral to orthorhombic and further to monoclinic with increasing the Nb concentration up to $x\ensuremath{\ge}0.2$. Interestingly, we observed dramatic changes in the magnetization ($M$) with increasing the Nb concentration, as the $M$ sharply increases below 10 K even at 2.5% substitution. Furthermore, ac susceptibility data show the spin glass behavior in $x=0.1$ sample. We find that the density of states near the Fermi level decreases and the activation energy increases, which results in the decreasing conductivity with higher Nb concentration. A significant shift in the peak position of ${A}_{2g}$ phonon mode has been observed using Raman spectroscopy, which indicates the change in the coupling due to the structural distortion with Nb substitution. The core-level photoemission study confirms that the Nb is present in $5+$ valence state. Our study reveals that the nonmagnetic ${\mathrm{Nb}}^{5+}$ (${d}^{0}$) substitution converts ${\mathrm{Co}}^{3+}$ ions to ${\mathrm{Co}}^{2+}$ and stabilizes both in the high-spin state. Our results suggest that structural and spin-state transitions as well as the difference in the ionic radii between ${\mathrm{Nb}}^{5+}$ and ${\mathrm{Co}}^{3+}$ are playing an important role in tuning the physical properties.

Effect of Nb content on the microstructure and corrosion resistance of the sputtered Cr-Nb-N coatings

Thin Cr-Nb-N films with Nb content ranging from 5.1 to 19.5 at.% were prepared onto the AISI 440C substrates by reactive magnetron sputtering of the Cr and Nb in Ar-N2 gas mixture. The effects of the Nb content on the microstructure and the corrosion behavior in 3.5 wt% NaCl solution were investigated. All the deposited films showed a typical surface feature of granular structure. The Cr-Nb-N films with 5.1 at.% and 10.9 at.% Nb showed a duplex layers consisting of a dense and coherent layer near film-substrate interface, followed by a columnar layer differed from the uniform columnar structure for pure CrN. While for Cr-Nb-N films with higher Nb content, there was no obvious dense layer but a columnar structure. The low Nb content Cr-Nb-N coated samples showed a positive shift of both corrosion potential and the pitting potential compared to the pure CrN coated sample while the pitting potential decreased for high Nb content Cr-Nb-N coated samples. The Cr-Nb-N film with Nb content of 10.9 at.% possesses the best corrosion resistance due to the high polarization resistance resulted from the modification of the microstructure by the Nb incorporation.

Genesis of the Paleoproterozoic Rare-Metal Granites of the Katugin Massif

We studied the petrography, mineralogy, and geochemistry of the Paleoproterozoic (2.06 Ga) granites of the Katugin massif (Stanovoy suture zone), which hosts the combined rare-metal Katugin deposit. Three groups of granites were distinguished: (1) biotite (Bt) and biotite–riebeckite (Bt–Rbk) granites of the western block of the massif; (2) biotite–arfvedsonite (Bt–Arf) granites of the eastern block; and (3) arfvedsonite (Arf), aegirine–arfvedsonite (Aeg–Arf), and aegirine (Aeg) granites of the eastern block. The Bt and Bt–Rbk granites of the first group are mainly metaluminous and peraluminous rocks with rather high CaO contents and the minimum F contents among the granites described here. It was suggested that the granites of this group could be derived from a source dominated by crustal rocks with a small addition of mantle materials. These granites probably crystallized from a metaluminous–peraluminous melt with elevated CaO and moderate F contents. Melts of such compositions are least favorable for the crystallization of ore minerals. The Bt–Arf granites of the second group are mainly peralkaline and show high contents of CaO and Y and low contents of Na2O and F. A mixed mantle–crust source was proposed for the Bt–Arf granites. The initial melt of the Bt–Arf granites could have a peralkaline composition with elevated CaO content and moderate to high F content. The Arf, Aeg–Arf, and Aeg granites of the third group are enriched in ore mineral and were classified as peralkaline granites with very low CaO contents, elevated Na2O and F contents, and usually very high contents of Zr, Hf, Nb, and Ta. Based on the geochemical and isotopic data, it was supposed that the source of the granites of the third group could be derivatives of basaltic magmas produced in an OIB-type source with a minor addition of crustal material to the magma generation zone. It was suggested that the primary melt of this granite group could be a peralkaline CaO-poor and F-rich silicic melt, which is most favorable for the crystallization of ore minerals. Based on the analysis of the geochemical characteristics of the three granite groups and their relationships within the Katugin massif, a qualitative model of its formation was proposed. According to this model, the Bt and Bt–Rbk granites of the western block crystallized first, followed by the Bt–Arf granites of the eastern block and, eventually, the Arf, Aeg–Arf, and Aeg granites enriched in ore minerals.

Extensional collapse of the Gondwana orogen: Evidence from Cambrian mafic magmatism in the Trivandrum Block, southern India

The assembly of Late Neoproterozoic–Cambrian supercontinent Gondwana involved prolonged subduction and accretion generating arc magmatic and accretionary complexes, culminating in collision and formation of high grade metamorphic orogens. Here we report evidence for mafic magmatism associated with post-collisional extension from a suite of gabbroic rocks in the Trivandrum Block of southern Indian Gondwana fragment. Our petrological and geochemical data on these gabbroic suite show that they are analogous to high Fe tholeiitic basalts with evolution of the parental melts dominantly controlled by fractional crystallization. They display enrichment of LILE and LREE and depletion of HFSE with negative anomalies at Zr–Hf and Ti corresponding to subduction zone magmatic regime. The tectonic affinity of the gabbros coupled with their geochemical features endorse a heterogeneous mantle source with collective melt contributions from sub-slab asthenospheric mantle upwelling through slab break-off and arc-related metasomatized mantle wedge, with magma emplacement in subduction to post-collisional intraplate settings. The high Nb contents and positive Nb–Ta anomalies of the rocks are attributed to inflow of asthenospheric melts containing ancient recycled subducted slab components and/or fusion of subducted slab materials owing to upwelling of hot asthenosphere. Zircon grains from the gabbros show magmatic crystallization texture with low U and Pb content. The LA-ICPMS analyses show 206Pb/238U mean ages in the range of 507–494 Ma suggesting Cambrian mafic magmatism. The post-collisional mafic magmatism identified in our study provides new insights into mantle dynamics during the waning stage of the birth of a supercontinent.

Physicochemical conditions of ore formation in the Samolazovskoe gold deposit (Central Aldan)

Using modern thermobarogeochemical methods (thermo- and cryometry, Raman spectroscopy, and LA-ICP-MS), we studied fluid inclusions in quartz from ores formed at the quartz-fluorite, pyrite-chalcopyrite, pyrite-molybdenite, and polysulfide stages of evolution of the Samolazovskoe gold deposit. We have established the fluid regime of the ore formation processes, the gas and liquid composition, main solid phases (metal sulfates, carbonates, and chlorides), homogenization temperatures of the inclusions, and the eutectic temperatures of their solutions. The obtained data helped to estimate the fluid temperatures during the formation of ores at each stage and to determine the contents of major salt components. Based on the substance solubility values given in the reference-book by V.B. Kogan, we have first constructed a phase diagram of the system Na2SO4-NaHCO3-H2O (Na2SO4 < 35 wt.%) at temperatures below 40 °C. The metal contents and geochemical specifics of solutions at each stage of the ore formation were determined by LA-ICP-MS. At the quartz-fluorite stage, the solutions were enriched in B, V, Co, Ni, Zn, As, Te, Cs, Ba, and Mg; at the pyrite-molybdenite stage, they had high concentrations of Ti, Ni, Nb, and Mo; and at the polysulfide stage, the solutions were rich in Ca, As, Pb, Sb, Te, Ag, Rb, Ba, and Sr. Native sulfur found along with sulfate and sulfide sulfur in the inclusions impelled us to study the sulfur isotope composition. The research has shown a light sulfur isotope composition (534S = -2.5 to -13.4%c). We believe that sulfide sulfur in the Samolazovskoe deposit formed from a fluid during high-temperature (>500-700 °C) sulfate reduction.

Geochronology and geochemistry of the granitoids and ore – forming age in the Xiaoyao tungsten polymetallic skarn deposit in the Jiangnan Massif tungsten belt, China: Implications for their petrogenesis, geodynamic setting, and mineralization

The Xiaoyao tungsten polymetallic skarn deposit in the eastern Jiangnan Massif of Yangtze Block is located at the contact between a granodiorite pluton and Sinian–Cambrian limestone. The intrusions in the tungsten-rich district comprise the Xiaoyao and other granodiorite plutons and granite porphyry dikes. The age determinations by LA–ICP–MS U–Pb dating of zircons indicate that the granodiorite formed at 149.4±1.1Ma, whereas the granite porphyry was emplaced at 133.2±0.7Ma. Re–Os dating of molybdenite from the skarn orebodies yielded a weighted average age of 148.7±2.3Ma (n=5). These ages indicate that the tungsten mineralization is temporally related to the granodiorite. The granodiorites are metaluminous (A/CNK=0.86–0.98) and in the high-K calc-alkaline series. They contain hornblende and have a negative correlation between P2O5 and SiO2, indicating that they are typical I-type intrusions. The granite porphyries exhibit high alkali contents (Na2O+K2O=7.97–9.53%), elevated FeOT/(FeOT+MgO) ratios (0.83–0.94), high concentrations of Zr, Nb, Ce, and Y, and high Zr saturation temperatures (average of 812°C); thus, they are geochemically similar to A-type intrusions. The initial 87Sr/86Sr and εNd(t) values range respectively from 0.7074 to 0.7083 and from −7.9 to −1.3 for the granodiorite, and from 0.7008 to 0.7083 and from −6.3 to −4.7 for the granite porphyry. In addition, two-stage Nd model ages (T2DM) of 1.0–1.6Ga for the granodiorite and 1.3–1.4Ga for the granite porphyry indicate that the Proterozoic crustal rocks of the Shangxi Group could have contributed to the Xiaoyao magmas. The rhenium contents of the molybdenite grains vary from 32 to 136ppm, suggesting that the molybdenum was derived mainly from a mixture of mantle and crustal sources. Based on the new geochemical data and regional geological investigations, we propose that the Late Jurassic mineralization-related I-type granodiorite was derived from the Neoproterozoic Shangxi metamorphic rocks with some additional input of mantle material. The magmatism was triggered by asthenospheric upwelling induced by slab tearing during oblique subduction of the paleo-Pacific plate beneath the South China Block.

Effects of Surface Tension Driven Convection Upon Crystal Growth of KTa1‐xNbxO3

AbstractThe surface tension driven convection, together with the rotating crystal growth process of potassium tantalate niobate (KTa1‐xNbxO3, KTN) crystals from unstirred melt has been carried out in a high temperature in‐situ observation system. The streamline of the stable convection is found to be in the form of a double loop axially symmetric vortices, which causes the rotation during KTN crystals growth process. The effect of surface tension convection on interfacial heat, mass and momentum transfer are investigated experimentally. The dimensionless parameters of the three transports are calculated. For KTN crystals, velocity and temperature boundary layers are pointless. Solute transfer is the main form of interface transport during crystal growth process. The effect of Nb content x on boundary layer thickness is discussed. There is a critical Marangoni Number . When , the concentration boundary layer becomes thinner with the increase of x as a result of weakened segregation effect. When , a thicker boundary layer emerges due to slower growth velocity under higher Nb contents. When , the influence of the two is comparable and the boundary layer can maintain a relatively steady value under different components.

Petrogenesis and metallogenic implications of Late Mesozoic intrusive rocks in the Tongling region, eastern China: a case study and perspective review

ABSTRACTLarge-scale Cu–Au mineralization is associated with Late Mesozoic intrusive rocks in the Tongling region of eastern China, which mainly comprise pyroxene monzodiorite, quartz monzodiorite, and granodiorite. To constrain the petrogenesis of the intrusive rocks and Cu–Au mineralization, detailed analyses of the geochronology, apatite in situ geochemistry, whole-rock geochemistry, and zircon Hf isotopic compositions were performed. Magmatic zircons from pyroxene monzodiorites, quartz monzodiorites, and granodiorites yield U–Pb ages of 136–149 Ma, 136–146 Ma, and 138–152 Ma, respectively, indicating that their formation ages are contemporaneous. Quartz monzodiorites and granodiorites (SiO2 = 57.9–69.5 wt.%) are highly potassic calc-alkaline rocks with adakitic affinity and have low MgO and Y contents, low zircon εHf(t) values (−11.7 to −39.0), high apatite Cl contents (>0.2 wt.%), and log fO2 values (−23.2 to −8.23), indicating that they may have formed when metasomatized mantle-derived magmas mixed with slab-derived magmas before undergoing crustal assimilation and fractional crystallization. Pyroxene monzodiorites (SiO2 = 48.4–53.0 wt.%) are shoshonitic and record high MgO, P2O5, and Y contents, high zircon εHf(t) values (1.55 to −7.87), high oxygen fugacity, low Nb and Ta contents, and low apatite Cl contents (mainly <0.2 wt.%), suggesting that they were primarily derived from a metasomatized lithospheric mantle-derived magma that experienced the assimilation of lower crustal materials. The results indicate that the intrusive rocks and associated large-scale Cu–Au mineralization of the Tongling region resulted from the partial melting of the subducted oceanic slab in an oxidizing environment.

Phase equilibria of the Ti-Al-Nb system at 1400 °C

Phase equilibria in the Ti-Al-Nb ternary system at 1400 °C was established, using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and electron probe micro-analysis (EPMA). No ternary compound was observed in this work. Compared with the calculated results, the α + β + γ three-phase region moves to higher Nb and Al contents and the σ + β + γ three-phase region moves to a lower Ti content in our experimental results. The tie-triangle of σ + δ + β moves to lower Ti and higher Nb contents. As a result, the homogeneity range of single α phase hugely expands to higher Nb and Al contents and the homogeneity range of single β phase region hugely expands to a higher Al content. The phase regions are also different with the previous reported experimental results.

Chemostratigraphy and evolution of the Paraná Igneous Province volcanism in the central portion of the state of Paraná, Southern Brazil

Analysis of borehole samples offers the potential to investigate the chemostratigraphic variations of a large igneous province in subsurface. New geochemical data based on multielement analyses of 829 chip samples that were obtained during the drilling of seven deep boreholes is presented for the central area of the Paraná Igneous Province (PIP). In order to detail the compositional variations found within the two main types from the Central-Northern Subprovince (CNSP), simple statistical treatment was carried out for part this database. Thus, the combination of low (L) and high (H) contents of Th, Nb, La and Yb was used as a means to create 16 geochemical subtypes for the Type 4 (LSi-LZr-HTi-HP) sequence. Likewise, other four elements (Cr, Ni, Cu and Pd) were selected with the same intention for the Type 1 (Central-Northern) (LSi-LZr-LTi-LP) sequence. When subtypes are plotted in the cross section, it is possible to observe that those with similar characteristics tend to be associated in groups (cycles). This analysis showed that the volcanic pile can be divided into at least eleven different cycles and also that they are laterally continuous throughout the section. The compositional changes observed in these volcanic cycles also display correlations with Mg#, Zr, Ti/Y and La/SmN ratios, for example. Therefore, since the reservoir is marked by periods of injection of more differentiated or more mafic magmas, it could be suggested that it was periodically recharged with batches of magma from the parental source.

Metal release and cell biological compatibility of beta-type Ti-40Nb containing indium.

Small indium (In) additions up to 5 wt % to the beta-type Ti-40Nb alloy effectively improve its mechanical biofunctionality. The impact on its biocompatibility is addressed in this work. Comparative electrochemical polarization studies and inductively coupled plasma optical emission spectrometry analyses were conducted in Tris-buffered saline (on the basis of 150 mM NaCl) with pH 7.6 and 2.0 at 310 ± 1 K with Ti-6Al-4V as reference. The metal ion releases from beta-type alloys were generally very low, for example, those of In3+ ions from (Ti-40Nb)-4In specimens were below 6 × 10-7 mmol/cm2 . X-ray photoelectron spectroscopy revealed the passivation mainly by Ti- and Nb-oxides with traces of In-oxides as the dominating surface process. In vitro studies demonstrate a better human bone marrow stromal cells (hBMSC) activity on the beta-type alloys in comparison to CP-Ti (grade 2), which is mainly due to their high Nb content. At 24 h after seeding on (Ti-40Nb)-4In the metabolic activity of hBMSC was 1.5-fold higher and after 11 days, the tissue non-specific alkaline phosphatase activity was 1.8-fold higher relative to values for CP-Ti. Surface treatments, like chemical etching or plasma oxidation, change the surface topography and the thickness and composition of the oxide layers, but they are not effective in further improving the cell response. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1686-1697, 2018.